Currently, scratch-off documents are used for a variety of applications. One of the most commonly used applications is the use of scratch-off documents for creating lottery tickets. In this application, a person purchases a lottery ticket and uses a hard object to scratch off the portion of the ticket covering hidden information such as a particular number. The use of scratch-off documents has vastly increased over the past years and several prior art documents address creating scratch-off documents.
In this regard, U.S. Patent Application 2007/0281224 is directed to a scratch-off document in which a first layer of toner forms an image and an optional barrier layer, typically clear, is deposited hereon. The first layer is well adhered to the substrate and the barrier layer is well adhered to the first layer. A second removable layer of toner is adhered to the first layer and can be removed when scratched using a hard object, leaving the first layer intact on the substrate. The application of the barrier layer is carried out offline and the document is reprinted with the scratch-off layer.
U.S. Patent Application 2008/0131176 is directed to an apparatus and method for producing a scratch-off document in which front side information containing the information to be hidden prior to scratch-off is first fused or otherwise adhered to the base material prior to the printing of a removable scratch-off layer.
U.S. Patent Application 2009/0263583 is directed to a scratch-off document in which the information layer includes both an indicia and a noise component of varying height. A scratch off layer is deposited over the noise component. This variable height functions to obscure the indicia so that it is not easily seen until scratched off.
U.S. Pat. No. 8,342,576 is directed to a scratch-off document having a first toner layer containing hidden information (i.e., the image that will eventually be revealed to the user after scratch off). The first layer is then covered by a printed, removable, waxy scratch-off layer having a distraction pattern.
Although each is satisfactory, cost efficiency improvements are always needed, as is the need for simple, but efficient scratch-off documents. In this regard, the prior art documents all use a plurality of fusing steps which is both costly and time consuming. The present invention overcomes these shortcomings by using two toner materials having different thermal conductivities so that only a single fixing step (or fusing step) is necessary.